The accurate estimation of precipitation type and accumulation has been a long-standing problem for operational meteorologists and hydrologists. When the estimates are obtained by weather radar, inaccuracies can result from radar miscalibration, attenuation of the signal in heavy precipitation, and the presence of non-meteorological scatterers such as ground returns, birds, and insects. Natural variations in the size, shape, and ice density of cloud and precipitation particles can also result in estimation uncertainties. Fortunately, many of these problems may be at least partially mitigated through the use of radar polarimetry.

As part of the evolution and future enhancement of the WSR-88D, the National Severe Storms Laboratory recently upgraded the KOUN WSR-88D radar to include polarimetric capabilities. Since this radar is the first in a possible future national network of polarimetric WSR-88D radars, it represents a significant advance in our ability to improve rainfall estimation and hydrometeor type classification on a large scale. In this paper, we describe polarimetric rainfall estimation and hydrometeor type classification techniques, provide examples of the polarimetric products, present initial impressions of the utility of the polarimetric upgrade to the WSR-88D radar, and discuss future plans for the operational demonstration of the KOUN radar’s capabilities.